The present invention relates to threaded fasteners and, more particularly, to anti-cross thread screws or fasteners with cleaning points.
When a screw or bolt is screwed into a threaded nut or port, where the port is subjected to foreign materials such as dust, dirt, weld splatter, paint or the like, the foreign material is carried into the mating area between the external and internal threads as the screw or fastener is threaded into the port. If foreign material is carried into the threads, galling and/or seizing usually results during assembly. This galling and seizing of the bolts causes substantial down time during an assembly operation, since the seize fastener must be removed, the hole cleaned out and a replacement fastener installed.
A common problem exists in the fastener field with cross threading. Cross threading generally occurs when the threaded fastener is received into a threaded nut or hole wherein the threads are in misalignment. Typical misalignments are axial and angular misalignments. In an axial misalignment, the axis of the shank of the screw is parallel with, but not colinear with, the axis of the receiving nut or hole. In an angular misalignment, the axis of the shank of the bolt is at an angle with respect to the axis of the nut or threaded hole. These misalignments cause the fasteners to be cross threaded and generally lead to seizing of the fasteners. The seizing causes a detrimental effect to both the bolt and nut, generally ruining one, the other or both, and causing little or no clamp load in the joint.
U.S. Pat. No. 4,952,110 illustrates an anti-cross threading screw. This fastener satisfactorily provides for anti-cross threading, but fails to provide a cleaning function. The present invention is an improvement over this patent. Accordingly, U.S. Pat. No. 4,952,110, the specification and drawings, is expressly herein incorporated by reference.
A traditional method of forming recesses or flutes onto a bolt is during the thread rolling operation. It requires a notch to be cut into the thread die, a fluter insert is positioned into the notch and as the part goes through the thread die, when it hits the fluter insert, it takes the form of the flute. A disadvantage in this type of method is that when the bolt goes through the thread die and hits the flute, it has a turbulent effect and the bolt wants to slip. A so-called drunken thread or a poor quality thread can result from this condition.
The method of the present invention provides forming the recess during the heading operation while forming the tip. By forming the recess or flute during the heading operation while forming the tip, when the part is placed into the thread die, there is no turbulence while the threads are applied on the bolt, thus forming good quality threads without the use of fluter inserts.